/*
	qfgl_ext.c

	QuakeForge OpenGL extension interface definitions

	Copyright (C) 2000 Jeff Teunissen <deek@dusknet.dhs.org>

	This program is free software; you can redistribute it and/or
	modify it under the terms of the GNU General Public License
	as published by the Free Software Foundation; either version 2
	of the License, or (at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

	See the GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to:

		Free Software Foundation, Inc.
		59 Temple Place - Suite 330
		Boston, MA  02111-1307, USA

	$Id$
*/

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#ifdef HAVE_DLFCN_H
# include <dlfcn.h>
#endif
#ifndef RTLD_LAZY
# ifdef DL_LAZY
#  define RTLD_LAZY     DL_LAZY
# else
#  define RTLD_LAZY     0
# endif
#endif

#ifdef _WIN32
// must be BEFORE include gl/gl.h
# include "winquake.h"
#endif

#ifdef HAVE_WINDOWS_H
# include <windows.h>
#endif

#ifdef HAVE_STRING_H
# include <string.h>
#endif
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif

#include "QF/qtypes.h"

#include "QF/GL/extensions.h"
#include "QF/GL/funcs.h"
#include "QF/cvar.h"
#include "QF/sys.h"

#include "r_cvar.h"

/*
	ParseExtensionList

	It takes a bit of care to be fool-proof about parsing an OpenGL extensions
	string. Don't be fooled by sub-strings, etc.
*/
qboolean
QFGL_ParseExtensionList (const GLubyte * list, const char *name)
{
	const char *start;
	char       *where, *terminator;

	// Extension names must not have spaces.
	where = (GLubyte *) strchr (name, ' ');
	if (where || *name == '\0')
		return 0;

	start = list;
	for (;;) {
		where = strstr (start, name);
		if (!where)
			break;
		terminator = where + strlen (name);
		if (where == start || *(where - 1) == ' ')
			if (*terminator == ' ' || *terminator == '\0')
				return 1;
		start = terminator;
	}
	return 0;
}

qboolean
QFGL_ExtensionPresent (const char *name)
{
	static const GLubyte *gl_extensions = NULL;

	if (!gl_extensions) {				// get and save GL extension list
		gl_extensions = qfglGetString (GL_EXTENSIONS);
	}

	return QFGL_ParseExtensionList (gl_extensions, name);
}


void *
QFGL_ExtensionAddress (const char *name)
{
	void       *handle;
	static qboolean glProcAddress_present = true;
#if defined(HAVE_GLX)
	static QF_glXGetProcAddressARB glGetProcAddress = NULL;
#else
	static void * (* glGetProcAddress) (const char *) = NULL;
#endif

#if defined(HAVE_DLOPEN)
	if (!(handle = dlopen (gl_libgl->string, RTLD_NOW))) {
		Sys_Error ("Couldn't load OpenGL library %s: %s\n", gl_libgl->string, dlerror ());
		return 0;
	}
#elif defined(_WIN32)
	if (!(handle = LoadLibrary (gl_libgl->string))) {
		Sys_Error ("Couldn't load OpenGL library %s!\n", gl_libgl->string);
		return 0;
	}
#else
# error "Cannot load libraries: %s was not configured with DSO support"
#endif

	if (glProcAddress_present && !glGetProcAddress) {
		if (QFGL_ExtensionPresent ("GLX_ARB_get_proc_address")) {
#if defined(HAVE_GLX)
			glGetProcAddress = QFGL_ProcAddress (handle, "glXGetProcAddressARB", false);
#elif defined (_WIN32)
			glGetProcAddress = QFGL_ProcAddress (handle, "wglGetProcAddress", false);
#endif
			if (!glGetProcAddress)
				glProcAddress_present = false;
		} else {
			glProcAddress_present = false;
		}
	}

	if (name && glProcAddress_present)
		return glGetProcAddress (name);
	return NULL;
}